Alastor

The Alastor is a living Devil Arm, the Thunder Sword and "Spirit of Lightning", appearing in Devil May Cry. It can only be wielded by the "chosen one" who can conquer it, but it is able to grant its wielder lightning speed and aerial capability.

Alastor the Thunder Devil
Dante finds Alastor impaled through the chest of a sculpture of an agonized woman, and it speaks to Dante of its intent to enslave him. It flies through the air and nails him to the ground, but he removes and subdues it.

Background
Alastor, meaning "Avenger", was a genius of familial feuds in classical mythology, and encouraged violent retribution. In Christian demonology, it became the chief executioner of Hell.

Trivia
Alastor's manifested spirit makes a cameo appearance as Blade Master Alastor in the Viewtiful Joe series. He holds a grudge against Dante for not bringing him to Dumary Island.

Dante wields the Alastor during his appearances in Viewtiful Joe, Viewtiful Joe: Red Hot Rumble and Shin Megami Tensei: Nocturne.

Alastor also appears as one of the final weapons for Date Masamune in Sengoku Basara 2 that there is six copies of Alastor that Date Masamune can use.